Transformers: Directing traffic on the electric highway

Send­ing pow­er to your home is a lot like dri­ving to a neigh­bor­ing state. You would­n’t con­sid­er tak­ing a two-lane sec­ondary road to trav­el to a city hun­dreds of miles away, would you? Of course not: You would find the near­est inter­state so you could dri­ve faster and arrive at your des­ti­na­tion in less time.

Just like you, your elec­tric­i­ty has an inter­state that allows it to trav­el long dis­tances, and a sec­ondary sys­tem that winds through back roads and neigh­bor­hoods to direct it to its final des­ti­na­tion, your home.

Trans­mis­sion lines that deliv­er pow­er from a pow­er plant to sub­sta­tions are the fast-mov­ing inter­state high­ways of the elec­tric indus­try. These lines car­ry from 44,000 to 100,000 volts of elec­tric­i­ty into the local dis­tri­b­u­tion sub­sta­tion. They are locat­ed on struc­tures rang­ing from large met­al tow­ers more than 100 feet tall to a sin­gle pole stand­ing 70 to 90 feet in the air.

And just like a car leav­ing the inter­state, the elec­tric­i­ty leav­ing the sub­sta­tion has to slow down when it enters the dis­tri­b­u­tion lines serv­ing YEC’s ser­vice area. Trans­form­ers in the sub­sta­tion pro­vide the brak­ing sys­tem for low­er­ing the volt­age of the elec­tric­i­ty so it can con­tin­ue safe­ly along its jour­ney.

So, how does it work? High­er-volt­age elec­tric­i­ty pass­es through a sys­tem of coiled wires locat­ed in the sub­sta­tion trans­former. The elec­tric­i­ty enters a pri­ma­ry side of the trans­former, which has met­al coil wind­ings sur­round­ing that side of the trans­former, and then pass­es to a sec­ondary side, which has few­er coil wind­ings. Trav­el­ing through the reduced num­ber of wind­ings low­ers the volt­age as it leaves the sec­ondary side and con­tin­ues the jour­ney along the dis­tri­b­u­tion lines.

The elec­tric­i­ty mov­ing along YEC’s dis­tri­b­u­tion lines is cruis­ing between 7,200 to 14,400 volts or 12,470 and 24,900 volts depend­ing on whether or not they are trav­el­ing along a sin­gle-phase or a three-phase line. Con­sid­er these lines the sec­ondary roads of the elec­tric sys­tem. They make the jour­ney through the local co-op’s ser­vice area.

Dis­tri­b­u­tion lines car­ry the elec­tric­i­ty short­er dis­tances than trans­mis­sion lines. They trans­port elec­tric­i­ty to the busi­ness­es, schools and homes served by your co-op. These are the lines you see YEC’s crews repair­ing after a storm.

Your elec­tric­i­ty has one more stop before mak­ing its way into your home. Just as you slow down to pull into your final des­ti­na­tion, the volt­age is low­ered one more time. It takes a turn off the dis­tri­b­u­tion line and into anoth­er trans­former that’s locat­ed out­side of your home. This trans­former may be a can­is­ter hang­ing on a pole or a box in your yard if you have under­ground elec­tric ser­vice. Trans­form­ers are pro­tect­ed by fus­es that will dis­con­nect them from the elec­tric line if there is a fault caused by cur­rent surges or over­loads.

After the cur­rent leaves the trans­former, it makes its way through a ser­vice line, into the meter base and to its final stop on the elec­tric highway—your home, where it pow­ers the appli­ances and elec­tron­ics of our mod­ern world.

Off like a shot

It sounds like a shot­gun going off or, as many peo­ple think, “a trans­former blow­ing,” but the blast you some­times hear just before an out­age is usu­al­ly a pro­tec­tive device for elec­tric cir­cuits called a fuse. A fuse locat­ed inside the bar­rel-shaped enclo­sure is what nor­mal­ly blows. For exam­ple, a tree limb falls on a line; the device does its job by open­ing the cir­cuit to lim­it the out­age. Fus­es are also installed atop co-op trans­form­ers to reduce the like­li­hood of real (and cost­ly) trans­former explo­sions.
Relat­ed Top­ics:
How YEC restores pow­er
South Lan­cast­er sub­sta­tion, trans­mis­sion lines under con­struc­tion